This invention relates generally to a combination lock and key security apparatus and, more particularly, to such an apparatus in which each of a plurality of keys uniquely activates wafer tumblers so as to control movement of a lock to different operational stations.
Conventional cylinder locks employ a key actuated plug rotatably mounted within a cylindrical housing. The plug typically retains a plurality of tumblers that are spring biased into engagement with an accommodating spline on the inner surface of the housing and thereby prevent rotation of the plug within the housing. Insertion of a properly bitted key into the plug draws the tumblers to shear positions and allows the plug to rotate into other positions. Additional rotation control of the plug often is provided by stop washers that rotate with the plug and engage stops on the housing so as to limit angular movement of the plug. A stop washer can in one case limit movement of the plug in only one direction from a locked position to a single unlocked station circumferentially spaced therefrom or can alternatively allow rotational movement in opposite directions from a locked position to a maximum of two operational stations circumferentially spaced therefrom. However, even in the latter case the direction of plug rotation and therefore access to either operational station is at the discretion of a user possessing the proper key.
Recent security developments, particularly in the field of locking electrical switches, require locks having a plurality of operational stations the access to each of which can be independently controlled. For example, many businesses now employ cash registers connected to computer systems that either receive or furnish financial and inventory data associated with individual transactions. It is often desirable in these instances that the access to specific input and output terminals of the computer system be limited to particular personnel responsible for given activities.
The object of this invention, therefore, is to provide a lock having a plurality of operational stations the access to each of which can be independently controlled.